fix(editor): missing signal of optional flat props (#13762)

Close https://github.com/toeverything/AFFiNE/issues/13750

#### PR Dependency Tree


* **PR #13762** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Optional block properties are now supported (e.g., flat-table), with
default values applied automatically when not set.

* **Bug Fixes**
* More reliable initialization and syncing of block properties, ensuring
defaults appear consistently.
* Change notifications now correctly reflect updates to
optional/defaulted properties.

* **Tests**
* Added tests verifying optional property behavior, default application,
syncing, and change events.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->





#### PR Dependency Tree


* **PR #13762** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

blocksuite/framework/store/src/model/block/flat-sync-controller.ts

@@ -47,6 +47,7 @@ export class FlatSyncController {
     }
 
     const model = schema.model.toModel?.() ?? new BlockModel<object>();
+    const defaultProps = schema.model.props?.(internalPrimitives);
     model.schema = schema;
 
     model.id = this.id;
@@ -55,7 +56,8 @@ export class FlatSyncController {
     const reactive = new ReactiveFlatYMap(
       this.yBlock,
       model.deleted,
-      this.onChange
+      this.onChange,
+      defaultProps
     );
     this._reactive = reactive;
     const proxy = reactive.proxy;
@@ -66,17 +68,6 @@ export class FlatSyncController {
       model.store = this.doc;
     }
 
-    const defaultProps = schema.model.props?.(internalPrimitives);
-    if (defaultProps) {
-      Object.entries(defaultProps).forEach(([key, value]) => {
-        if (key in proxy) {
-          return;
-        }
-        if (value === undefined) return;
-        proxy[key] = value;
-      });
-    }
-
     return model;
   }